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Archive for the ‘STEM’ Category

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SciTech Tuesday: Plutonium’s discovery

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Plutonium, the element used to power the Fat Man bombs used for the test at Trinity and for the

This metal ring is an alloy of plutonium in a form that is used in nuclear warheads.

This metal ring is an alloy of plutonium in a form that is used in nuclear warheads.

bombing of Nagasaki, was discovered on February 23rd, 1943. A group of scientists at UC Berkeley bombarded uranium with deuterons (the nucleus of a heavy hydrogen isotope, made up of a proton and a neutron), and observed that it had an atomic number of 94 and was chemically distinct from uranium. This team, led by Glenn Seaborg, sent a research paper describing their investigation to a journal, but publication was delayed until after World War II for security reasons. Theoretical calculations by researchers at the Cavendish Laboratory in England indicated that plutonium (Pu in the periodic table) could be used for powerful critical nuclear reactions, and would be produced as a by-product in uranium reactors.

Much of the Manhattan Project’s efforts were to create plutonium, and to separate it from uranium. It did prove to be a better source of fission energy than uranium. Today’s nuclear weapons have plutonium cores.

Plutonium is very reactive, and in air will form a flaky substance that spontaneously ignites. Because it is so reactive it is toxic, and unlike uranium accumulates in bones. These properties make it much more dangerous than uranium.

This is the plutonium based power module of the Mars Rover.

This is the plutonium based power module of the Mars Rover.

239Pu is the isotope used primarily for fission. It has a half-life of about 24,000 years. 238Pu has an extremely high decay heat, and so is often used to produce special generators that use heat to power satellites and space probes. It has a half-life of about 88 years. 240Pu has a high spontaneous fission rate, and so is not suited for weapons use. There are two other isotopes of plutonium (241Pu and 242Pu) that mostly present radiation hazards in waste. All isotopes decay to an isotope of uranium but 241Pu (becomes an isotope of americium).

As an expert in plutonium, Seaborg was placed on leave from Berkeley and sent to work at the

A young Glenn Seaborg posing in front of a Periodic Table showing gaps which would eventually be filled with elements he would help discover.

A young Glenn Seaborg posing in front of a Periodic Table showing gaps which would eventually be filled with elements he would help discover.

ChicagoMetallurgical Laboratory (a secret part of the Manhattan Project) for the duration of the war. The discovery of plutonium was only a small part of his illustrious career. He was involved in the discovery of several other elements, became chancellor at UC Berkeley, was chairman of the US Atomic Energy Commision, and served on the presidential commission that produced the famous Nation at Risk report on the failings of educational policy in the US. He won the Nobel Prize in Chemistry in 1951 and died in 1999.

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: Heavy water on Fat Tuesday

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In our museum’s collection (2006.232) is a rusty barrel which spent decades at the bottom of a cold Norwegian lake before being recovered and donated in a ceremony at the Inaugural International Conference on World War II.

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What makes this rusty barrel special, and how did it end up at the bottom of that lake? It held heavy water, and was being transported to Germany from a plant in occupied Norway, when the boat carrying it was sunk by resistance forces supported by the allies.

What is heavy water, and why is it important enough for it to be an object of sabotage? Let’s examine a timely analogy.

Today is Tuesday. There are lots of Tuesdays, the second weekday of the week. Some Tuesdays are special. The first Tuesday of November in a leap year is  the occasion of Presidential elections in the United States. One Tuesday of every year is very special in New Orleans and some other parts of the world, as it is designated Mardi Gras (or Fat Tuesday). So there are lots of Tuesdays, most common, and a few with a small peculiar characteristic that puts them in a group as a kind of Tuesday. So some Tuesdays are different than other Tuesdays, but still Tuesdays nonetheless. Here in New Orleans, 2% of Tuesdays are Mardi Gras, and about 0.5% of Tuesdays are presidential election days.

The same is true of chemical elements. Elements are arranged in the periodic table according to their structure. What makes one element different from others is the number of protons in its nucleus. A quick examination of a periodic table of the elements shows that while there are only 7 days of the week, there are 118 elements. But just like some Tuesdays are special, some atoms of an element are special too.

For example, let’s talk about uranium. Uranium is an element with a very large nucleus. It has 92 protons in its nucleus. All atoms with 92 protons are uranium. Atoms will normally have as many electrons as protons, but they can gain or lose electrons and still be the same elements (atoms that have gained or lost electrons have a charge and are called ions). The last component of the structure of an atom is a neutron. Neutrons are in the nucleus with the protons. In elements the number of neutrons tends to increase along with the number of protons. Uranium usually has 143 neutrons (99.3% of the time). Sometimes it has 146 neutrons (0.7% of the time). The atomic weight of an atom is equal to the number of neutrons and protons it has, so these two forms of uranium have atomic weights of 235 and 238, respectively. Forms of elements that differ in the number of neutrons in their nucleus are called isotopes. Isotopes of an element are indicated by their atomic weight. So those two elements of uranium are called 235U and 238U.

Many elements have isotopes. Carbon normally has an atomic weight of 12 (12C), but has an isotope of 14C (used in radiocarbon dating). Oxygen is typically in the form of 16O but an isotope 18O is used in paleoclimatology to estimate past temperatures. Some isotopes are radioactive, like 14C and 238U, but others like 18O are not. Radioactive isotopes break down into other elements and give off energy at a constant rate (14C has a half life of 5730 years, and 238U of 4.5 billion years). Not all radioactive isotopes are dangerous (14C gives off very little energy, and 238U gives off a whole lot).

So you could say that Mardi Gras is an isotope of Tuesdays. It has more mass than most Tuesdays, primarily because of the extra king cake and beads. Perhaps we should designate it as Mardi GrasTuesday.

That brings us to heavy water. A water molecule is formed when two hydrogen atoms are bonded to one oxygen atom. Hydrogen is the simplest element. Most hydrogens have one proton and one electron. An isotope of hydrogen has a proton and a neutron in the nucleus (2H, also called deuterium). Water made from this isotope of hydrogen is called heavy water.

The German effort to develop nuclear weapons used a nuclear reactor design that required heavy water. A nuclear reactor uses a sustained and controlled nuclear chain reaction. To control the reaction the reactor has to have a substance that absorbs neutrons. The reactors also produce a great deal of heat and so require a coolant (nuclear electrical generation plants use the heat from the reactor to make steam). In the reactors designed by German scientists in the 1940s heavy water was used to absorb neutrons and cool the reactor. The reactors designed by Enrico Fermi and other scientists in the Manhattan project used graphite to absorb neutrons and normal water for coolant.

Today heavy water is used in reactors that depend on unenriched uranium. Enriched uranium has a higher concentration of 238U. They tend to produce more plutonium and tritium as byproducts than other reactors. Since plutonium is key to most contemporary nuclear weapons, these kinds of plants are often used to produce weapons material.

In 1934 a Norwegian plant began producing fertilizer and heavy water as a byproduct. The plant used electrolysis to create ammonia. Electrolysis can also be used to separate heavy water from from typical water. German nuclear scientists had been unsuccessful at using graphite in their plants (they had unknowingly used impure graphite), and so were in search of heavy water. Before the war started French intelligence was trying to remove the heavy water in Norway from German access. After Germany took over both France and Norway the allies attempted to destroy the plant in late 1942. Air attacks on the plant convinced the Germans to move the operation to the homeland. That’s when the resistance made its strike.

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech-Tuesday: Manhattan’s Moles–espionage in the race to build atomic weapons

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During the Manhattan Project, the military and intelligence officials worked hard to protect the secrecy of the effort. With 400,000 employees, and 600 contracting companies, this was a big challenge. Overall, many aspects of the security effort were successful. The vast majority of employees had no idea what they were working on, and very few people had knowledge of more than the small portion of the effort in which they were involved. Undercover investigators across the country posed as hotel employees, electricians, and exterminators to monitor employees and gather information.

Most of the focus of investigation was on persons of German descent or Nazi sympathizers, and in this the security effort made a grave error. Although there were attempts by German infiltrators to sabotage power plants supplying project sites, there was little penetration by the Nazis of the Manhattan project.

Soviet espionage was much more effective.

The Soviet effort against Hitler’s Empire cost many millions of lives, and strained a young and relatively weak economy. Stalin had a personal trust in Churchill and Roosevelt, but the relationship between the allies was based on common interests and fears, not common principles and values. When Roosevelt died, any trust Stalin had for the US went to the grave with him. When Churchill was replaced as Prime Minister in England, his allies in the West were gone.

Movies like Mission to Moscow and Song of Russia portrayed Soviet society favorably, because they were designed to as a form of propaganda to support the war effort. Citizens and institutions in the US and UK were generally distrustful of communists and Soviets in particular.

And yet there was an undercurrent of pro-communism in American and English society as well. Some people felt strongly, especially in the context of the Great Depression, that capitalism had failed ordinary people. Others, who may not have understood all the technical details of the atomic weapons being developed, did see that unilateral possession of such dangerous tools could create instability and usher in a new era of dangerous imperialism.

Klaus Fuchs looking wistful in his Manhattan Project ID photo

Klaus Fuchs looking wistful in his Manhattan Project ID photo

Klaus Fuchs was a physicist in the Manhattan Project. He had fled Germany in the 1930s, and attended university in Bristol and Edinburgh, before being briefly detained as a German National at the start of the war. In 1942 he became a British citizen, but had already volunteered his services as a spy to the Soviet embassy. While working at Los Alamos on the bomb construction and mechanism, he passed information on to Moscow. After the war he returned to England and continued to work in nuclear arms development, and passed to the Soviets information about the hydrogen bomb. Intelligence in the US and UK managed to decode Soviet transmissions, and gathered information using them(called the Venona cables). This intelligence led to the arrest, conviction, and later deportation of Fuchs to East Germany.

Theodore Hall’s history is a little more surprising. His family suffered from deprivation and anti-Semitism in the Great Depression (thus he changed his family name Holtzberg). He entered Harvard young as a prodigy, and graduated at 18, and by 19 was the youngest scientist in the Manhattan Project. He was a Marxist, and while working on nuclear technology became very concerned about its dangers to society. While on leave in New York in 1944, Hall contacted the Soviets and promised to keep them informed of developments at Los Alamos. He used coded references to poems from Walt Whitman to communicate with another spy, Harry Gold. Gold couldn’t identify Hall, and so Hall continued his career as a scientist unhindered. It wasn’t until the release of documents after the fall of the Soviet Republic that his role was uncovered.

Harry Gold was a chemist who had been communicating industrial secrets to the Soviets since 1935. When FBI investigators found a classified map of Los Alamos in his apartment he confessed and implicated David Greenglass.

David Greenglass in his mugshot.

David Greenglass in his mugshot.

David Greenglass was an Army draftee working at Los Alamos as a machinist. He passed on drawings of the implosion trigger mechanism, stuffing them in a Kleenex box for a courier to pick up. Greenglass was the brother-in-law of Julius Rosenberg.

Julius Rosenberg was one of the most famous spies of US history. He worked at the US Army Signal Corps Engineering Labs at Fort Monmouth, where research on radar and communications was conducted. He was fired after the Army discovered he had formerly been a member of the Communist Party.

A natty Rosenberg at his arrest.

A natty Rosenberg at his arrest.

Although both Julius and his wife were convicted of espionage for stealing nuclear secrets, there is no evidence today that Ethel was involved at all. Documents released after the fall of the Soviet Union indicate that Julius passed information about radar and electronics to the Soviets. The Rosenbergs were executed by electrocution in 1953. The judge sentencing them, blamed the Korean War on them.

It’s not quite the Bourne series, but these individual stories hold fascinating details (a Kleenex box? Leaves of Grass?). They also seem to belie the idea that spies act for mercenary purposes, or national allegiance. Most of these individuals acted because of some principles or values that crossed national boundaries.

All images from Wikimedia Commons

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: Niels Bohr announces fission of uranium

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Yesterday was the 75th anniversary of the 5th Washington Conference on Theoretical Physics. This meeting on the 26th of January 1939 may seem an obscure point in history. Fifty-one physicists from around the world gathered at George Washington University, which co-sponsored these conferences with the Carnegie Institute. A statement published in Science on the 24th of February 1939 contained this paragraph:

“Certainly the most exciting and Important discussion was that concerning the disintegration of uranium of mass 239 into two particles each of whose mass is approximately half of the mother atom, with the

Niels Bohr at 37, when he won the Nobel Prize for Physics

Niels Bohr at 37, when he won the Nobel Prize for Physics

release of 200,000,000 electron-volts of energy per disintegration. The production of barium by the neutron bombardment of uranium was discovered by Hahn and Strassmann at the Kaiser-Wilhelm Institute in Berlin about two months ago. The interpretation of these chemical experiments as meaning an actual breaking up of the uranium nucleus into two lighter nuclei of approximately half the mass of uranium was suggested by Frisch of Copenhagen together with Miss Meitner, Professor Hahn’s long-time partner who is now in Stockholm. They also suggested a search for the expected 100,000,000-volt recoiling particles which would result from such a process. Professors Bohr and Bosenfeld had arrived from Copenhagen the week previous with this news, and observation of the expected high-energy particles was independently announced by Copenhagen, Columbia, Johns Hopkins, and the Carnegie Institution shortly after the close of the Conference. Professors Bohr and Fermi discussed the excitation energy and probability of transition from a normal state of the uranium nucleus to the split state. The two opposing forces, that is, a Coulomb-like force tending to split the nucleus and a surface tension-like force tending to hold the “liquid-drop” nucleus together, are nearly equal, and a small excitation of the proper type causes the disintegration.” (Science, vol 89 number 2304, page 180)

It could be argued that this was the starting point of the Manhattan Project. Niels Bohr, the winner of the 1922 Nobel Prize for his work on atomic structure, spoke about the the first observed, and explained, observation of nuclear fission. Enrico Fermi, who had won his Nobel Prize just a few months before, was there to discuss this announcement.

Three and a half years later, Fermi would build a reactor under the football field at the University of Chicago and create the first sustained chain reaction of uranium fission, and be a primary scientist in the Manhattan Project. Fifteen months later Bohr was under Nazi rule in occupied Denmark—he escaped the Nazis in dramatic fashion in September 1943 when he learned they had plans to arrest him, and left on a fishing boat for Sweden. From Sweden he went to England, where he joined the Tube Alloys project. In December of 1943, under the alias of Nicholas Baker, he traveled to the US to meet with Gen. Groves, and scientists at Los Alamos.

Over the next two years Bohr traveled frequently to Los Alamos, where he acted as a mentor to the young scientists, much as he had in the years before the war at his institute in Copenhagen.

Niels Bohr at 25, with his wife Margrethe, on the occasion of their engagment.

Niels Bohr at 25, with his wife Margrethe, on the occasion of their engagment.

Niels Bohr was a brilliant and fascinating man. He risked his life to save others, working for years to get scientists and technicians of Jewish ancestry out of Europe. He developed a model for the structure of the atom, and when it was surpassed, said “there is nothing else to do than to give our revolutionary efforts as honourable a funeral as possible.” He was a scientist who could see past his own ambitions and accomplishments, and helped develop a community of colleagues whose collaboration exceeded their individual efforts.

After the war, Bohr returned to Copenhagen and ran the institute which now bears his name-The Niels Bohr Institute at the University of Copenhagen. He won the Atoms for Peace award in 1957 for his efforts to build an international agency on atomic weapons and energy. He died in 1962, at age 77.

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: Plutonium in the Desert

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In late January of 1943 General Leslie Groves decided on a site for the third major research and production site of nuclear materials. On February 9th 1943 the military approved financing for building a facility in central Washington, on the banks of the Columbia River. The development of the Hanford site might be the greatest building project of the war effort.

With the development of facilities in Oak Ridge Tennessee (26 miles from Knoxville), and the Argonne Lab in Illinois (24 miles from Chicago), there were concerns about proximity to population centers in making new sites. In fall of 1942 Groves recruited DuPont to develop a plutonium production facility. Taking a very patriotic position, DuPont insisted that they not receive any profits or patents from the operation. With many technical requirements in mind, DuPont engineers searched for a site to build a huge operation around large reactors that would convert uranium to plutonium.

They settled on 670 square miles in the arid part of Washington, where the Yakima, Snake, and Columbia rivers meet. The area was isolated, although there were settlements of farmers and Native Americans. The presence of the large Columbia River flow was important to sight selection. The 1500 locals were relocated so that no one lived closer than 10 miles to the reactor and isolation units. DuPont moved quickly, breaking ground in March of 1943. DuPont employed 44900 construction workers on a site that eventually included 25 dormitories and 4300 family housing units to build and run Hanford during the war years. The campus grew to 554 buildings, including 3 nuclear reactors and 3 plutonium separation facilities, with 386 miles of roads, 125 miles of railways, and 4 electrical substations at a cost of $230M by the end of 1945.

The construction of the B reactor, designed by Fermi, began in August 1943. The B reactor was the first reactor built to produce plutonium (which was only discovered in 1940). It used about 180 tons of uranium slugs surrounded by graphite (to absorb emissions and control the nuclear reaction) and water from the Columbia piped through more than 2000 aluminum tubes (to cool the reactor) at a rate of 75000 gallons per minute. The used water was held in ponds for a few hours before being released back into the river. The construction of the reactor took about a year—by late September of 1944 the B reactor was producing plutonium.

Under the right conditions (bombardment by neutrons) uranium 238 will become first very unstable uranium 239, then decay to somewhat more stable neptunium, which decays to plutonium. Only a very small amount of the uranium will become plutonium in this process, so the uranium slugs need to be removed from the reactor, chemically treated to remove the plutonium, and then returned to the reactor for more processing.

DuPont developed several technologies to make and improve the reactors at Hanford in the war years. When they developed the next two reactors (B and D added in 1944 and 1945) they added ammonia cooling of the water before it entered the reactor. They also developed teflon and closed-circuit cameras to more easily conduct repairs and replacement of parts in areas of the plant where workers could not go because of high radiation. The chemical separation process also was managed remotely.

The radiation inside the plant contaminated all the parts used to build it. They became radioactive too. In fact, the water released in the Columbia was also contaminated. Over decades the reactors at Hanford created a lot of environmental contamination in accidental air releases, groundwater contamination, and release into the river. Today Hanford is the site of some major research operations and power generation, but it is also our country’s biggest hazardous waste site.

The first batch of plutonium from the B reactor was ready February 2nd 1945 and arrived in Los Alamos on the 5th. The bomb tested at Trinity and Fat Man (detonated on Nagasaki) used plutonium from the Hanford reactors. Reactors B, D, and F continued operation into the 1960s.

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

all photos from the Wikimedia Commons.

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SciTech Tuesday: The Manhattan Project goes critical—Roosevelt approves funding for plants to deliver uranium, plutonium, and heavy water

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A timeline of the events in the Manhattan Project’s history might be laid out in a logarithmic scale. As often happens in big projects things happen slowly at first and build, with progress coming more quickly, until a critical threshold (often visible only in hindsight) is passed. It could be argued that the critical point for the Manhattan Project was December 28th, 1942.

A fact that may not be known to many is that the project to build an atomic weapon began well before the U.S. entry into WWII. The letter from Albert Einstein and Leo Szilard to President Roosevelt warning of potential German development of a bomb using nuclear fission was delivered in August of 1939. Within 2 months Roosevelt had a Uranium Committee meeting to discuss the feasibility of an American effort. About 18 months later a government sponsored committee recommended more research, and while the British committee determined that building a bomb was possible. Based largely on the British report, in October of 1941 Roosevelt asked Vannevar Bush to investigate what it would take, and how much it might cost to build a fission-powered bomb. A month later the government sponsored committee declared such a project feasible, and a month after that was Pearl Harbor. In January of 1942 Roosevelt told Bush to begin development of the effort to build a nuclear bomb. Over the next several months plans bounced around between scientific committees debating the best plans for producing enough fissionable material. The primary arguments were between using uranium or plutonium (only discovered by Glen Seaborg in early 1941, but believed to be easier to bring to critical mass), and the methods to separate uranium isotopes to get pure Ur235. The basic structure of the Manhattan Project, with Groves directing it, Robert Oppenheimer leading the scientific mission, and the primary sites in Los Alamos, Hanford, and Oak Ridge, also developed in the last half of 1942.

So when Bush brought to Roosevelt plans to build facilities in December of 1942 the project was over 3 years old, and other than plans, there was not a lot to show for it. Roosevelt’s signature put an amazing effort in motion.

By the end of 1943 the three sites are fully staffed and mostly built. In early 1944, 200 g of Ur235 is shipped from Oak Ridge to Los Alamos, and models of bombs are built and tested. In August of 1944 Bush informs General Marshall that bombs will likely be ready by August of 1945. A month later Colonel Tibbets’ bomb squadron starts practicing with dummy bombs called ‘pumpkins.’

In early 1945 Los Alamos got its first plutonium from Hanford. Two weeks after Roosevelt dies (in other words late April of 1945) President Truman is briefed on the Manhattan Project. In July of 1945 the first atomic bomb is tested at Trinity. Just barely ahead of schedule, less than two years after Roosevelt approved the $2 billion project, two bombs are ready for use against Japan.

Another interesting thing to note about the project timeline, is the early moves by scientists and politicians to try to contain a potential arms race. This began in September of 1944 when Vannevar Bush and James Conant began to lobby for international agreements on atomic research, and continues with the Franck Report in June of 1945, written by scientists in the Chicago lab.

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

all photos from the Wikimedia Commons.

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SciTech Tuesday: The other enigma–why Nazi science never developed a nuclear weapon.

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Almost all the research that lead to the idea that an atomic weapon could be built occurred in Germany in the 1930s. As of 1939, of all the major labs doing atomic research, only Chadwick’s (in Liverpool) was not in Germany, or territory soon to be occupied by Germany. The experiments that uncovered the phenomenon of nuclear fission were conducted in Berlin just before the beginning of the war. In addition, Germany controlled great resources of uranium and heavy water, which were necessary for developing the bomb.

Yet Nazi science made very little progress towards a nuclear weapon during the war.

One popular, but unlikely, explanation is that Heisenberg sabotaged the effort. The true reason is probably more complicated.

Heisenberg did report to organizers of the effort that creating a sustained chain reaction was probably years away, and very challenging. This was in 1938 and 1939, after the discovery of fission, and following his visit Bohr in occupied Copenhagen. But this may have been more because of his lack of interest in engineering, and an orientation towards theoretical questions that led to shortsightedness. After all, the Manhattan project succeeded, with arguably lesser scientists.

Comparing the Manhattan Project to the Nazi effort is probably a fruitful way to look for answers.

The Manhattan project succeeded because theoretical scientists envisioned the possibility, engaged powerful politicians in the idea, and those politicians then engaged people with great organizational and leadership skills in assembling the scientists and resources necessary to meetthe challenge.

Vannevar Bush, U.S. Office of Scientific Research and Development wanted one person with power and skill, to lead the effort to develop an atomic weapon. Leslie Groves was recommended to him as that man. With the help of Robert Oppenheimer, who was also a systems thinker, Groves orchestrated an all-out effort to assemble a diverse team and get them everything they needed. Oppenheimer found theoreticians and empiricists and engineers with the knowledge, ability, and willingness to do the work. He also developed plans that laid out multiple methods to achieve each step necessary for success. For example, the Manhattan Project pursued multiple bomb and fuel designs right to the end of weapon development. Fat Man (dropped on Nagasaki) and Gadget (tested at Trinity) were implosion-type bombs with a plutonium core. Little Boy (dropped on Hiroshima) used a uranium core and a gun-type detonator. It is also critical to note that from 1939 when Roosevelt set up the Uranium Committee until 1942 when the Manhattan Project was formed, most of the work done was politicking and feasibility studies. And, finally, many of the scientists and engineers working on the project were immigrants from countries occupied by Germany, and who had fled fascism and war.

The Nazi effort to build a bomb was not so well designed. The first organization to develop atomic weapons, or Uranprojekt, was directed by physical chemist at the University of Hamburg, Paul Harteck. This first group was disbanded when the invasion of Poland led to the call of the scientists involved into military training.  The military then started its own project, and included in it Walther Bothe, Hans Geiger, Otto Hahn, and Heisenberg. The Kaiser Wilhelm Institute was made part of the project under military control. They made separate divisions of the project, and divided the work across several institutes, each with their own research agenda.

In 1942, about when the U.S. was forming the Manhattan Project, Germany removed their effort from military control, reassigned scientists to what was considered more pressing work, and refocused the nuclear project on energy development instead of weapons development. Hermann Goring, who had developed the aviation engineering effort so successfully, was put in charge, hoping that he could be successful in this project as well.

In June of 1942, a lab in Leipzig working on chain reactions exploded, possibly because of a hydrogen leak, destroying the facility most advanced in developing a critical reactor under German control. Six months later Fermi’s experimental pile in Chicago went critical, and the path to critical mass and sustained reactions became clearer for the Manhattan Project.

In the end, Goring’s leadership did not improve the Uranprojekt’s success. The effort was too fractured, and the almost endless supply of young scientists available to the Allied effort was not allowed to the Nazi effort, as many young technicians and scientists were conscripted as troops.

It required some hubris to succeed at building the bomb. Oppenheimer and Groves viewed each challenge in the long and complex path to success as points to plan for, and achievements to develop towards, and not as obstacles. It was the all-out philosophy, and the ability to see both the forest and the trees that led to the success of the Manhattan Project.

 

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Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

all photos from the Wikimedia Commons.

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SciTech Tuesday–Nuclei are sticky drops, not brittle solids, and that leads to The Bomb

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For most of World War II, like in all of previous human history, people used energy stored in the bonds of molecules for power. But in December of 1938, a chain of events began that changed the way we use chemicals for energy—and human history changed drastically.

This diagram shows how a neutron entering the nucleus of uranium creates an unstable isotope, which breaks down into two other elements and releases protons and a great deal of energy.f

This diagram shows how a neutron entering the nucleus of uranium creates an unstable isotope, which breaks down into two other elements and releases protons and a great deal of energy.f

Chemistry and knowledge about the structure of atoms developed by leaps and bounds in the early 20th century. In 1869 Dimitri Mendeleev showed that all chemical elements can be grouped and organized using regular patterns in their characteristics. The Periodic Table of Elements was a huge innovation that allowed systematic investigation into the nature of atoms and elements. JJ Thomson’s discovery of the electron, and the modern atomic theory, began to reveal why those patterns in the Periodic Table existed.

The discovery that some elements had different forms with different masses (in 1913) led to the concept of isotopes (a term created by Margaret Todd) and a rush of investigation into the nucleus of atoms. From the work of Thomson on, much of the empirical work into the structure of atoms involved aiming electrons or radiation at them to see what would happen. This is how Ernest Rutherford discovered the atomic nucleus (1911), and the proton (1918). In 1932 Alex Chadwick described the neutron, and the full complement of atomic particles was available to theoreticians and chemists to explain quantum mechanics and chemical reactions.

Norman Feather bombarded nitrogen with neutrons, and found that the result was boron and alpha radiation. After this, neutrons were used to examine materials to look for heavier elements and radioactive elements. In the mid-1930s a research team led by Otto Hahn, Lise Meitner, and Fritz Strassman had found many new products when they exposed uranium to a beam of neutrons. Atomic theory had developed by thinking of all elements as more complicated forms of hydrogen, and as brittle material from which small parts might be chipped off. So scientists expected to break large atoms up by knocking off small parts when they shot them with neutrons. Lise Meitner had to flee to Sweden, since she was Jewish, and the lab was in Germany, but Hahn and Strassman continued the experiments and shared with her their data.

This was the setup used for the experiments by Hahn, Meitner, and Strassman, later replicated by Frisch. By today's standards it's very primitive.

This was the setup used for the experiments by Hahn, Meitner, and Strassman, later replicated by Frisch. By today’s standards it’s very primitive.

In experiments with uranium exposed to a beam of electrons from December 16-17 1938, Hahn and Strassman found that the products were not forms of uranium, but were instead barium. On December 19th Meitner received a letter from Hahn describing the results. He was at a loss to explain how the atoms lost 40% of their mass. Meitner trusted that Hahn had identified the element correctly—after all he was an excellent analytical chemist. She understood the physics better than he did. Meitner also recalled that Marie Curie and her lab often found barium in samples of decayed radioactive material. She also knew that pioneers like Niels Bohr had described the nucleus as more like a liquid drop than a solid. Making some calculations, Meitner saw that the charged nucleus could in fact split into two large pieces. She saw also that the mass of the two resulting nuclei would be less than the mass of the original nucleus. Rather than being a problem, this difference in mass was more evidence that the nucleus had split. Einstein’s theory of relativity suggested that matter could be converted into energy. She made some more calculations and discovered that the missing matter could explain the huge energy that had been released in the transformation.

Lise Meitner worked with her visiting nephew Otto Frisch to write a detailed explanation of what they thought had happened in the experiment. When Frisch returned to his lab he reproduced the experiment and showed that they were correct in their interpretation. Meitner named the splitting of the nucleus ‘fission,’ after the splitting of cells in organisms. In 1944 Hahn, but not Meitner, was awarded the Nobel prize for the discovery of fission.

This new form of chemical manipulation—the splitting of nuclei instead of the splitting of molecules by breaking the covalent bonds between them—provided millions of times more energy. In just seven years this energy was used to make the world’s first three atomic bombs.

If you are a middle school science teacher, and would like to spend next summer learning about STEM and history, consider joining us for Real World Science – Yesterday, Today, and Tomorrow, a week-long teacher seminar this July. Sign up for email updates here.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: Werner Heisenberg–good or bad? It’s uncertain.

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Werner Heisenberg was born on December 5th 1901. The co-founder and pioneer of quantum mechanics was born to parents in Bavaria, where his father taught and studied classical languages. In his youth Heisenberg was a member of the German Youth Movement, and showed aptitude for both mathematics and physics. A Rockefeller Foundation fellowship took him to Copenhagen for a year in 1924 to conduct research with Niels Bohr. Returning to Germany, he developed the first parts of the quantum theory with collaborators. In 1926 Heisenberg returned to Copenhagen and work with Bohr, as a lab assistant and lecturer.

In 1927 Heisenberg wrote to his colleague Wolfgang Pauli about what came to be called the uncertainty principle. He moved to Leipzig as a professor that same year. Shortly after he wrote papers with Pauli describing relativistic quantum theory, and in 1932 Heisenberg was awarded the Nobel Prize for Physics.

With the rise of fascism and anti-semitism in Germany, quantum physics and all theoretical physics, including relativity, were derided. Reports in the press referred to Heisenberg as ‘white jew.’ Political forces were set on denying academic advancement to Heisenberg. Just before the outbreak of the war, in 1939, he visited the United States, and refused an invitation to emigrate. Heisenberg’s mother was friends with Himmler’s mother, and she made an appeal. Himmler wrote a letter supporting Heisenberg, saying that Germany could not afford to lose or silence a man it needed to educate a generation of scientists, and signed it ‘in friendship, Heil Hitler.’ Privately, Himmler warned Heisenberg to be cautious.

Right after Meitner and Frisch explained the experimental results that showed the fission of uranium, Heisenberg became a principal scientist in the Uranium Club—Germany’s nuclear energy project. In 1941 He traveled to German-occupied Copenhagen to speak with Niels Bohr and his colleagues. When he returned to Germany, Heisenberg presented a lecture to Reich officials on the feasibility of developing nuclear power, and the Army subsequently cut its funding for the project. In a meeting in 1942 with the German Minister of Armaments, Heisenberg described nuclear weapons as being expensive to develop (in terms of money and manpower) and unlikely to be successful before 1945.

In early 1943 he received an endowed chair in physics in Berlin. He moved to the city, but evacuated his family and most of his research staff to the country to avoid bombing. Heisenberg traveled to Copenhagen after Bohr escaped, and later to Switzerland. In 1945 he joined his family and staff outside of Berlin.

On May 3rd 1945, Heisenberg was captured by American forces who invaded his country estate while the area was still under German control. He was removed from Germany and taken to England, and didn’t see his family for several months. Part of the goal of this mission to acquire German scientists and their research before the Russians obtained them. Heisenberg resumed his position at the head of German physics research after the war, leading the Max Planck Institute (renamed from the Kaiser-Wilhelm Institute, and relocated from Berlin to Munich).

Some historians view Heisenberg as a hero, who used subterfuge to derail the German nuclear program. Others see him as a patriot with conflicted feelings about his government.

He died of cancer at his home in February of 1976.

Heisenberg was handsome and stylishly dressed as a young man.

Heisenberg was handsome and stylishly dressed as a young man.

If you are a middle school science teacher, and uncertain what to do next summer, consider joining us for Real World Science – Yesterday, Today, and Tomorrow, a week-long teacher seminar this July. Sign up for email updates here.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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SciTech Tuesday: So a General, a Major, and a Communist from Berkeley walk out in the desert…

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In November 1942, a General, a Major, and a Communist from Berkeley walked into the desert…And they came out with a plan to make a facility that would build the first nuclear bombs.

It was fall of 1942, and the Manhattan Project had already become the biggest science and engineering project in US History. It would eventually cost $2 billion in contemporary dollars (about 26 billion today) and employ about 130,000 people. But it had not grown to its full extent yet, and it needed sites and facilities. Research at UC Berkeley and the University of Chicago would continue, but other projects were too dangerous or too secret to take place in cities on university campuses.

General Leslie Groves had spent his last several years overseeing the construction of the Pentagon. Although he did an excellent job, he found it exhausting, and was hoping for what he considered the relative peace of war duty as a next assignment. Instead he was given the reins of the Manhattan Project.

Groves knew his first step should be to find a director of the scientific project—someone to lead and oversee all the scientific and technological aspects of the work. His choice was Robert Oppenheimer, a theoretical physicist whose friends and relatives (and wife!) were all members of the Communist Party. Groves found strong resistance from military security, and further concerns that all these Nobel scientists would be led by someone without such distinction. Groves argued that Oppenheimer was a genius who could understand all aspects of the project, that all the other possibilities were occupied on their own projects, and that the Manhattan Project had a bad reputation, limiting the pool of interested parties.

Groves is now considered a genius for choosing Oppenheimer, but at the time the opinion weighed more on the side of crazy. Groves and Oppenheimer met with Vannevar Bush in Washington DC, and the appointment was made.

In October, work had begun to build a huge facility at Oak Ridge, Tennessee to enrich Uranium using a gaseous separation process. Land had been purchased in June to build a facility in Illinois to produce Plutonium. Delays in construction of the Illinois facility led to Fermi’s work under the University of Chicago football field. The success of that experiment convinced authorities to build a lab that later relocated a short distance to become Argonne National Laboratories. Another production facility for plutonium would be built in central Washington on the banks of the Columbia River in January of 1943. It later became Hanford Nuclear Reservation. Other sites, smaller and spread throughout the country and Canada, were developed as well.

There remained the need for a facility where the actual construction of the working bombs would take place. Oppenheimer had a country home in Albuquerque, New Mexico, and loved the high and dry desert of northern New Mexico. Nothing could be more remote, and thus secure, and he believed the beauty of the landscape would inspire the scientists brought there. He suggested the region as a possible site to General Groves. The two men visited it with Major John Dudley, a surveyor. The purchase of the site was approved before the end of November 1942, and after spending $7 million the site of almost 50,000 acres was completed in November of 1943.

This would become the site where Otto Frisch almost caused a meltdown with stacks of Uranium bricks. It was where the three bombs, one tested at Trinity, and two deployed over Japan, were designed and built. It was where Richard Feynman went out dancing and drumming at night, causing rumors that an Indian spirit haunted the hills. Argonne, Hanford, Los Alamos, and Oak Ridge remain as important government research and military facilities, but Los Alamos remains the most isolated of them.

Check out our new special exhibit, Manufacturing Victory, where you can see that Manhattan Project Patch and many other cool artifacts from the Home Front, where folks made all the stuff we used to win the war.

Posted by Rob Wallace, STEM Education Coordinator at The National WWII Museum

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